It has been conventional practice in building structural buildings for both residential and commercial use to form the major portions of heating and cooling ducts using sheet metal such as galvanized sheet steel. The ducts must be fabricated on the job site by metalworking personnel who must cut and shape the sheets to size to form the ducts and associated headers to lead to registers located in both floors and walls as well as ceilings. Many prior art forms of such ducts and headers have tried to provide insulated ductwork in the form of sheets, but virtually all forms have been either too costly or difficult to install in a timely and efficient manner. Many have involved sheets having spacer means therewithin for creating air gaps between roofs and ceilings, and insulation by providing the sheet with corrugations and insulating material.
The use of sheet metal in forming ductwork is expensive and time-consuming in the construction of buildings requiring special skills for metalworking and its installation. Such all-metal ducts experience damage due to dampness which can and does occur in the ducts resulting in deterioration of the ducts and adjacent wooden members such as floors and joists. The all-metal ducts have no insulating value unless some form of insulating material be additionally provided. The ducts when employed to carry heated or cooled air experience uncontrolled expansion and/or contraction which cause undesirable sound effects when the ducts create small to large unexpected and irregular boomlike effects. The dampness, over time, also causes rusting of the ductwork and its attachment means such as nails or staples.
In addition to the aforesaid types of metal sheeting for ductwork, other forms of heat-reflective insulation can be manufactured in collapsed form, such as being rolled upon itself into a compact cylindrical roll, for storage and transportation. The insulation can be unrolled and expanded for insulation by attachment to adjacent structural members such as floor and ceiling joists in a building. The insulation is folded in such a manner that the material in flat form, which may be folded by accordion pleats, can be cut to size for installation in lengthy runs as required. Such material is intended to provide heat reflective insulation of predetermined dimensions to fit within the framework of a building with marginal edge portions for attachment to structural members. Such insulation is intended to serve an insulating purpose only and is not designed to provide ductwork as such. Actually, it does not have the structural strength, or rigidity to form ductwork, deflectors or headers in heating or cooling systems.
In the manufacture and use of metal sheet material for ductwork, the material is normally called "panning material" for forming such ducts and headers leading to forced air or gravity flow air registers in floors, walls and ceilings. The term "panning" has become a generic word in the trade for material which is used in flat form in many cases and is bent into various shapes and contours for customized ductwork depending upon the structural requirements of the particular building.
Accordingly, it is a primary object of this invention to provide a structural panning material or board for forming ductwork and headers, the material being rigid and yet plyable, moistureproof, fireproof and smokeproof for such purposes.
Another object of this invention is to provide a new and improved panning material which is economical to manufacture and install in many shaped contours in forming ducts and headers, the material being simplified in design, fireproof, strong and durable for long-term use for the intended purposes. The material combines the best features of corrugated paper board and heat-reflective metallic foil exterior surfaces as well as scored side edge portions for ready installation in both planar and angled relation.
A still further object of this invention is to provide a durable moistureproof, fireproof and smokeproof structural panning material which is relatively rigid yet plyable and bendable to form various configurations of heating and cooling ducts, and header members which are utilized therewith, the material having a substantial bursting strength and a suitable fire resistance rating for safe and approved use in both residential and commercial buildings.